Technical Field of the Invention
The present invention relates to novel cosmetic compositions for topical application, in particular for the photoprotection of the skin and/or the lips and/or superficial body growths/hair against ultraviolet radiation (such compositions hereinafter simply being designated antisun or sunscreen compositions), and to the use of same for the cosmetic applications indicated above.
More especially, this invention relates to novel cosmetic compositions exhibiting improved photoprotective capacity, comprising, formulated into a cosmetically acceptable support therefor: (i) at least one silicon compound bearing a benzotriazole function substituent and constituting a lipophilic organic sunscreen, and (ii) a specific judiciously selected oil, present in a predetermined amount, and which comprises a benzoic triacid triester.
Description of the Prior Art
It is known to this art that light radiation of wavelengths of from 280 nm to 400 nm permits tanning of the human epidermis and that light radiation of wavelengths of from 280 to 320 nm, i.e., UV-B irradiation, causes skin burns and erythema which may be harmful to the development of a natural tan; this UV-B radiation should thus be screened from the skin.
It is also known to this art that UV-A radiation, of wavelengths of from 320 to 400 nm, promotes tanning of the skin, but is also liable to induce an adverse change therein, especially in the case of sensitive skin or skin which is continually exposed to solar radiation. UV-A rays in particular cause a loss of elasticity of the skin and the appearance of wrinkles, promoting a premature aging of the skin. Such irradiation promotes triggering of the erythemal reaction or amplifies this reaction in certain individuals and may even be the cause of phototoxic or photoallergic reactions. It is thus desirable to also screen out UV-A radiation.
Many and varied cosmetic compositions for the photoprotection (UV-A and/or UV-B) of the skin are known to this art.
These known sunscreen compositions contain, in various concentrations and depending on the nature of the pharmaceutical form selected, one or more standard lipophilic and/or hydrophilic organic screening agents capable of selectively absorbing harmful UV radiation, these screening agents (and the amounts thereof) being selected as a function of the desired protection factor (the protection factor (PF) being expressed mathematically as the ratio of the irradiation time required to reach the erythema-forming threshold with the UV screening agent to the time required to reach the erythema-forming threshold without UV screening agent).
Lipophilic UV organic screening agents which are particularly advantageous in antisun cosmetics and which are highly active both in the UV-A range and in the UV-B range are described in EP-A-0,392,883; EP-A-0,660,701; EP-A-0,708,108; EP-A-0,711,778; EP-A-711,779.
These are silanes or polyorganosiloxanes substituted by a benzotriazole function. They present the particular feature but also the drawback of being solid at room temperature. Consequently, including same in an antisun cosmetic composition entails certain constraints as regards their formulation and implementation, in particular as regards determining solvents for properly dissolving them. In this respect, oils are typically selected such as esters, and more particularly C.sub.12 -C.sub.15 alkyl benzoates ("Finsolv TN" marketed by Finetex), or triglycerides and in particular C.sub.8 -C.sub.12 fatty acid triglycerides ("Miglyol 812" marketed by Huls), or monoalcohols or polyols such as ethanol, as well as mixtures thereof. Although providing solubilizing properties with respect to the aforesaid screening agents, these solvents nevertheless present the drawback of themselves having no intrinsic activity as regards screening out UV radiation, whether UV-A or UV-B irradiation.
Utilizing oils of the benzoic triacid triester type such as tridecyl trimellitate is known for the formulation of many cosmetic products comprising a fatty phase. Compare, in particular, EP-A-0,792,637 relating to lipsticks and EP-A-0,194,055 relating to the preparation of anhydrous cosmetic formulations free of mineral oil.
U.S. Pat. No. 4,940,577 describes this type of oil as constituting the fatty phase of transparent microemulsions of the water-in-oil type having a low water content and necessarily containing a specific phosphate ester as the sole emulsifier. These microemulsions are useful as antisun products based on organic UV screening agents such as octyldimethyl para-aminobenzoate, octyl cinnamate, octyl salicylate or 3-benzophenone, as well as self-tanning products.
And U.S. Pat. No. 4,940,574 describes this type of oil as an emollient in anhydrous antisun products having a high degree of protection, containing, in a silicone oil, a combination of two UV-B organic screening agents selected from among a cinnamate, a salicylate and a para-aminobenzoate and a UV-A organic screening agent of the benzophenone type.